Chess Ratings

A
chess rating is a number used to indicate the estimate playing strength of the
chess player based on the player’s performance against other players.

A
higher number usually indicates a stronger player.

Players' ratings go up if they perform better
than expected and down if they perform worse than expected. The magnitude of
the change depends on the rating of their opponents

The FIDE Elo rating system uses statistical
formulas to measure the chess skill of a player by calculating the relative
skill levels of players in a game. The creator, Arpad Elo, a Hungarian-born
American physics professor, was a master-level chess player himself. The system has improved so much so that Elo
rating can predict the outcomes of chess games with high consistency and
reliability. For example, if player A has an Elo rating 245 points more than
player B, the chances are player A will score 4 out of 5 points against player
B. If the difference in rating is 200 points, the score is reduced to 3 out of
4 points. This reliability of prediction is a result of a very reliable rating
system.

If a junior player who had a rating of 1010 before chess
coaching and improved his
rating to 1443 after three months of training, it allow chess coaches and players to measure and
monitor the effectiveness of their training programs.